The present invention generally relates to an apparatus and a method for cleaning a conduit that has chemical substances deposited on its inside wall and more particularly, relates to an apparatus and method for cleaning an exhaust conduit that has chemical substances coated on its inside wall by using a shaft equipped with scraping elements that is capable of moving in both the radial and the vertical direction, the apparatus may further include fluid nozzles and a vacuum means to facilitate the removal of such substances.
In the chemical industry, many processes conducted in a fabrication plant require the treatment of effluent or exhaust gases from a process machine. The treatment is necessary to either complete a chemical reaction such that non-reacted chemicals are not released into the atmosphere, or to convert toxic or flammable components of the exhaust gases into non-toxic and non-flammable components before they are released into the atmosphere. The treatment of effluent gases is especially important in the semiconductor fabrication industry since most of the process gases utilized in the industry are either highly toxic or highly flammable.
As an example, a conventional controlled decomposition/oxidation (or CDO) system 10 that is equipped with recirculation and sump pump is shown in FIG. 1. The system 10 is supplied by the Delatech Corp. as an exhaust gas conditioning equipment. The system 10 is effective in treating or scrubbing exhaust gases through a thermal reaction section 12 and a cooling/scrubbing section 14. Exhaust gases 18 from a semiconductor process machine enter into the system through inlets 20 and are first treated in an oxygenation reaction section 22. The oxygenated exhaust gases then enter the thermal reaction section 12 which is heated by a heating elements 24. The heating element 24 is powered by an electric wiring fed through wiring connector 26 and controlled by thermocouple 28. The thermally reacted exhaust gases then enter into a primary cooling/scrubbing section 30 which is equipped with a scraping element 34 and a water supply pipe 36. Cooling water (not shown) is sprayed through a nozzle opening 38 in order to cool off the high temperature thermally reacted exhaust gases. The temperature of the thermally reacted exhaust gases can reach above 800xc2x0 C. and therefore must be cooled before it is processed by the secondary cooling/scrubbing section 14. The scraping element 34 is constructed of a spiral metal blade which can be moved up and down by the shaft 42. The vertical motion of the scraping element 34 is designed to remove the chemical substances that have been cumulated and deposited on the inside wall 46 of the exhaust conduit 54 which is the lower part of the thermal reaction section 12. These chemical substances include a variety of high temperature films, nitride powers and films, etc. A hard and highly resilient film is normally formed by these chemical substances. Cooled exhaust gases then enter the secondary cooling/scrubbing section 14 and are treated by the scrub packing 48 before it is released to the atmosphere through an outlet 52. The apparatus is effective for treating exhaust gases from a semiconductor fabrication process that contain toxic elements by first treating in a high temperature oxygenation reaction, then converting to a lower temperature and then converting the toxic substances into non-toxic substances such that they can be safely released into the atmosphere.
In the apparatus shown in FIG. 1, it has been found that while the usage of the apparatus achieves the desirable result of toxic gases conversion, the deposition of hard chemical substances on the inside wall 46 of the thermal reaction section 12 cannot be avoided. The conventional cleaning apparatus which is equipped with the scraping element 34 and the water spray nozzle 38 is not effective in cleaning the exhaust conduit 54. The spirally constructed scraping element 34 which is designed to have a maximum diameter slightly smaller than the inside diameter of the exhaust pipe 54, cannot adequately clean the inside wall 46 of the exhaust conduit 54. FIG. 2 is a view illustrating that the cleaning apparatus 32 has been removed from the exhaust conduit 54. The cleaning apparatus 32 moves only in the vertical direction to cause a rotational movement of the spiral scraping element 34 to scrape the inside wall 46 of the exhaust conduit 54. The cleaning of the inside wall 46 therefore cannot be effectively executed by the spiral blade 34. This is especially the case when after an extended period of operation, a hard deposit layer formed of chemical substances is adhered to the inside wall 46 and becomes very difficult to remove. When the thickness of the hard deposit layer becomes excessive, it sometimes jams the scraping blade 34 such that the exhaust gas treatment process has to be stopped and the machine has to be serviced.
It is therefore an object of the present invention to provide an apparatus and a method for cleaning a conduit that has chemical substances deposited on its inside wall that do not have the drawbacks and shortcomings of the conventional apparatus and method.
It is another object of the present invention to provide an apparatus and a method for cleaning a conduit that has chemical substances deposited on its inside wall by using a movable shaft and a plurality of scraping elements mounted on the shaft for cleaning the inside wall of the conduit.
It is a further object of the present invention to provide an apparatus and a method for cleaning an exhaust conduit that has chemical substances deposited on its inside wall by using a movable shaft equipped with a plurality of scraping elements that can move not only in a vertical direction but also in a radial direction.
It is another further object of the present invention to provide an apparatus and a method for cleaning an exhaust conduit that has chemical substances deposited on its inside wall by using a shaft equipped with a plurality of scraping elements that is capable of making vertical and radially oscillating movements for cleaning the chemical substances.
It is yet another object of the present invention to provide an apparatus and a method for cleaning an exhaust conduit that has chemical substances deposited on its inside wall by using a shaft that is equipped with a plurality of scraping elements and fluid nozzles for removing the chemical substances by spraying a cleaning fluid during the cleaning process.
It is still another object of the present invention to provide an apparatus and a method for cleaning an exhaust conduit that has chemical substances deposited on its inside wall by using a shaft equipped with a plurality of scraping elements for removing the chemical substances, and a vacuum device for removing the debris of such chemical substances.
In accordance with the present invention, an apparatus and a method for cleaning an exhaust conduit that has chemical substances deposited on its inside wall are provided by using a shaft equipped with a plurality of scraping elements that is capable of making vertical and radially oscillating motions against such chemical substances such that they can be effectively removed from the exhaust conduit.
In a preferred embodiment, an apparatus for cleaning a conduit that has chemical substances deposited on its inside wall is provided which has a movable shaft that has an upper portion and a lower portion, a plurality of scraping elements attached to the upper portion of the shaft, a drive means attached to the lower portion of the shaft for providing radial and vertical motions of the shaft, a housing adapted for receiving the shaft and the plurality of scraping elements and for collecting debris of the chemical substances during cleaning, and a controller for controlling the cleaning process.
In another preferred embodiment, an apparatus for cleaning an exhaust conduit is provided which includes a shaft that has an upper portion and a lower portion, a plurality of scraping elements attached to the upper portion of the shaft, a plurality of fluid nozzles provided in the upper portion of the shaft, a drive means that is attached to the lower portion of the shaft for providing motions in the radial and vertical directions, a housing for receiving the shaft end the plurality of scraping elements, and a controller for controlling the cleaning process.
The present invention is further directed to a method for cleaning a conduit that has chemical substances deposited therein which can be carried out by the operating steps of first providing a shaft that has an upper end and a lower end, the upper end of the shaft has a plurality of scraping elements attached thereto and the lower end of the shaft is attached to a drive means for providing radial and vertical motions to the shaft, the shaft and the drive means are mounted in a housing adapted for connecting to the conduit, then connecting the housing to the conduit, and then moving the shaft in a radial or vertical motion for removing the chemical substances from the inside wall of the conduit.